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6 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Y(CuO2)2 by Materials Project

(CuO2)(Y)(CuO2) crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Y3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Y–O bond distances ranging from 2.39–2.41 Å. There are two inequivalent Cu+2.50+ sites. In the first Cu+2.50+ site, Cu+2.50+ is bonded in a square co-planar geometry to four O2- atoms. There is two shorter (1.90 Å) and two longer (1.92 Å) Cu–O bond length. In the second Cu+2.50+ site, Cu+2.50+ is bonded in a square co-planar geometry to four O2- atoms. There is two shorter (1.90 Å) and two longer (1.91 Å) Cu–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to two equivalent Y3+ and two Cu+2.50+ atoms to form a mixture of distorted corner and edge-sharing OY2Cu2 tetrahedra. In the second O2- site, O2- is bonded to two equivalent Y3+ and two Cu+2.50+ atoms to form a mixture of distorted corner and edge-sharing OY2Cu2 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Y(CuO2)2 by Materials Project

(CuO2)(Y)(CuO2) is Spinel structured and crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Y3+ is bonded to four O2- atoms to form YO4 tetrahedra that share corners with twelve CuO6 octahedra. The corner-sharing octahedra tilt angles range from 60–61°. All Y–O bond lengths are 2.15 Å. There are two inequivalent Cu+2.50+ sites. In the first Cu+2.50+ site, Cu+2.50+ is bonded to six O2- atoms to form CuO6 octahedra that share corners with six equivalent YO4 tetrahedra and edges with six CuO6 octahedra. There are two shorter (2.06 Å) and four longer (2.08 Å) Cu–O bond lengths. In the second Cu+2.50+ site, Cu+2.50+ is bonded to six equivalent O2- atoms to form CuO6 octahedra that share corners with six equivalent YO4 tetrahedra and edges with six equivalent CuO6 octahedra. All Cu–O bond lengths are 2.05 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to one Y3+ and three Cu+2.50+ atoms to form a mixture of distorted corner and edge-sharing OYCu3 tetrahedra. In the second O2- site, O2- is bonded to one Y3+ and three equivalent Cu+2.50+ atoms to form a mixture of distorted corner and edge-sharing OYCu3 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on KY(CuO2)2 by Materials Project

KY(CuO2)2 crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. K1+ is bonded to eight equivalent O2- atoms to form distorted edge-sharing KO8 hexagonal bipyramids. All K–O bond lengths are 2.90 Å. Y3+ is bonded in a body-centered cubic geometry to eight equivalent O2- atoms. All Y–O bond lengths are 2.41 Å. Cu2+ is bonded in a square co-planar geometry to four equivalent O2- atoms. All Cu–O bond lengths are 1.95 Å. O2- is bonded in a 6-coordinate geometry to two equivalent K1+, two equivalent Y3+, and two equivalent Cu2+ atoms.

36 MATERIALS SCIENCE↗
NASA NTRS1987

Superconductivity above 90 K in the square-planar compound system ABa2Cu3O(6 + x) with A = Y, La, Nd, Sm, Eu, Gd, Ho, Er, and Lu

Superconductivity has been found in the 90-K range in ABa2Cu3O(6 + x) with A = La, Nd, Sm, Eu, Gd, Ho, Er, and Lu in addition to Y. The results suggest that the unique square-planar Cu atoms, each surrounded by four or six oxygen atoms, are crucial to the superconductivity of oxides in general. In particular, the high Tc of ABa2Cu3O(6 + x) is attributed mainly to the quasi-two-dimensional assembly of the CuO2-Ba-CuO(2 + x)Ba-CuO2 layers sandwiched between two A layers, with particular emphasis in the CuO(2 + x) layers. Higher-Tc oxides are predicted for compounds with bigger assemblies of CuO2 layers coupled by Ba layers.

Hor, P. H.↗
DOE OSTI2020

Materials Data on Ba2Y(CuO2)4 by Materials Project

YBa2Cu4O8 crystallizes in the orthorhombic Cmmm space group. The structure is three-dimensional. Ba2+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of Ba–O bond distances ranging from 2.76–3.12 Å. Y3+ is bonded in a distorted q6 geometry to two equivalent Cu+2.25+ and eight O2- atoms. Both Y–Cu bond lengths are 2.42 Å. There are four shorter (2.56 Å) and four longer (2.57 Å) Y–O bond lengths. There are two inequivalent Cu+2.25+ sites. In the first Cu+2.25+ site, Cu+2.25+ is bonded in a square co-planar geometry to four O2- atoms. There are a spread of Cu–O bond distances ranging from 1.87–1.94 Å. In the second Cu+2.25+ site, Cu+2.25+ is bonded in a 5-coordinate geometry to one Y3+ and five O2- atoms. There are a spread of Cu–O bond distances ranging from 1.98–2.07 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded to four equivalent Ba2+ and two Cu+2.25+ atoms to form a mixture of distorted edge and corner-sharing OBa4Cu2 octahedra. The corner-sharing octahedral tilt angles are 17°. In the second O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Ba2+, two equivalent Y3+, and two equivalent Cu+2.25+ atoms. In the third O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Ba2+, two equivalent Y3+, and two equivalent Cu+2.25+ atoms. In the fourth O2- site, O2- is bonded in a distorted T-shaped geometry to two equivalent Ba2+ and three equivalent Cu+2.25+ atoms.

36 MATERIALS SCIENCE↗
NASA NTRS1990

Preparation and characteristics of superconducting cuprate thin films: Nd(2-x)Ce(x)CuO4 and substituted Bi-system

Characteristics of the electron-doped-type Nd(2-x)Ce(x)CuO4 systems and substituted Bi2(Sr,Ln)3Cu2Oy system were systematically studied using the high quality thin-film samples. The Nd(2-x)Ce(x)CuO4 thin films with various Ce concentrations, x, were prepared by RF magnetron sputtering on SrTiO3 heated at around 500 C. After subsequent annealing at 1100 C in air, the films showed the c-axis orientation normal to the substrates. By means of the reducing treatment (annealing in a vacuum), superconductivity was induced for the films with 0.14 is less than or equal to x is less than or equal to 0.18. The superconductivity and transport properties of the films were strongly affected by the reducing treatment. The x = 0.15 film exhibited a sharp superconducting transition with zero resistivity at 22 K, in consistent with the diamagnetic properties. The resistivity of the films was fairly low with metallic characteristics, and the sight of the Hall coefficient was negative in the normal state. On the other hand, the normal-state optical measurements showed that the undoped Nd2CuO4 is a semiconductor with a charge transfer gap of 1.3 eV, and that, when Ce ions were doped, a plasma reflection due to the free-carriers came to be seen with the plasma frequency of 1.07 eV for 0.14 is less than or equal to x is less than or equal to 0.18. Moreover, x ray photoemission study revealed that the Cu valence of the film decreased for 2(+) for x = 0 to 1(+) for x = 0.15. These physical properties are in contrast with those of hole-doped-type cuprate superconductors. Bi2(Sr,Ln)3Cu2Oy thin films were also prepared on MgO substrates heated at 600 to 700 C by similar methods. It was found that the growth conditions for Bi-systems with two CuO2 planes were different for each composition and species of lanthanoid in the films. Moreover, preparation of Bi-system with three CuO2 planes was very difficult when lanthanoid atoms were doped in the system. Their electric transport properties and x ray photoemission spectroscopy were investigated. Carrier concentration and Cu valence were discussed with regard to the superconductivity.

Adachi, H.↗